1. Field of the Invention
The present invention relates to the technology of detecting the speed of a motorcycle and transmitting detected data to the speedometer of the motorcycle and more particularly, to a motorcycle wheel speed transmission mechanism that fits an electronic speedometer and facilitates maintenance and repair works.
2. Description of the Related Art
A conventional motorcycle wheel speed transmission mechanism, as shown in FIG. 6, comprises a gear housing 2 affixed to the front fork of a motorcycle and coupled to one end 32 of the axle tube 31 at the front wheel hub 3 of the motorcycle, a driven gear 21 pivotally mounted in the gear housing 2 and having cut planes 211 on the periphery at one end, an output gear 22 pivotally mounted in the gear housing 2 at one side and meshed with the driven gear 21, a transmission cable 24 connected between the output gear 22 and a mechanical speedometer of the motorcycle, a driving ring 23 that has internal cut planes 231 respectively abutted against the cut planes 211 and external lugs 232. When the axle tube 31 is rotating during running of the motorcycle, protruding lugs 32 of the axle tube 31 are forced to move the external lugs 232 of the driving ring 23 and the driven gear 21, thereby causing rotation of the output gear 22, and therefore the transmission cable 24 is rotated with the output gear 22 to move the internal mechanism of the mechanical speedometer.
The aforesaid prior art design has drawbacks as follows:
1. The design is suitable for use with a mechanical speedometer, not practical for use with an electronic speedometer.
2. When the components are covered with dust after a long use or damaged, the maintenance or repair work takes much time and labor.
3. Using the transmission cable 24 to move the internal mechanism and index of the mechanical speedometer mechanically shows a significant error.
U.S. Pat. No. 7,078,891B2 discloses a speedometer gear output structure, which includes a gearbox installed in a motorcycle and holding a driven gear and an output gear for synchronous rotation with the wheels of the motorcycle, an annular magnetic device fastened to the gear shaft of the output gear for synchronous rotation, and a circuit board mounted in the gearbox and holding a sensor corresponding to peripheral magnetic zones of the annular magnetic device for outputting an output signal indicative of the speed of rotation of the output gear. This design eliminates the drawback of the aforesaid conventional mechanical design. However, because the circuit board is mounted in the gearbox, the cover of the gearbox and the related sealing structure must be detached for allowing removal of the circuit board from the gearbox when the sensor failed and a repair work is necessary. After the repair work and re-installation of the circuit board, the gearbox must be sealed gain. It takes much time and labor when a maintenance or repair work of the sensor is necessary.